#include<stdio.h>
#include<math.h>
void main()
{
	float x1,x2,a;
	scanf("%f",&a);
	x1=a;
	x2=(x1+a/x1)/2;
	while(fabs(x2-x1)>=1e-5)
	{
		x1=x2;
		x2=(x1+a/x1)/2;
	}
	printf("%f",x2);
}
